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Abstract Ultimate and proximate analyses, HHV and BET surface area have been assessed in the unburned materials obtained by combustion in a conical spouted bed of four types of vegetable biomasses representative of forestry residues, grass and food industry. The results show that the materials are mainly of carbonaceous structure, which stems from the incomplete decomposition of cellulose and lignin, and their content decreases with combustion temperature. The unburned materials have a high surface area, which is of the same order as certain commercial active carbons, rendering them suitable properties for use as low-cost adsorbent. In order to verify this fact, removal efficiencies have been determined in amoxicillin removal tests, and the characteristic parameters, as well as mass transfer coefficients, have been calculated for two adsorption models following Langmuir and Freundlich isotherms. The results confirm that this byproduct obtained in the recovery of energy from waste biomass performs well in the removal of emerging pollutants from wastewater, and is a viable alternative of commercial adsorbents.

Abstract Phosphate removal from wastewater and the correspondent sustainable technologies are urgent issues to solve since phosphorous causes eutrophication of water sources. The effect of heat treatment on the mixture eggshell (ES), rich in calcium carbonate, with fiber palm (F), rich in carbonaceous material for phosphate removal is here reported focusing on the effects of temperature and F/ES ratio. The gases obtained from the F pyrolysis process help to improve the Ca(OH)2 formation. In samples with a ES/F ratio of 1/10 (ESF-1:10) the CaCO3 is mainly transformed into Ca(OH)2 (83 %) at 600 °C instead of 800 °C. The obtained solids were employed for phosphate removal from aqueous solutions and characterized before and after P removal. The ESF-1:10 sample pyrolyzed at 600 °C exhibited the best adsorption performance (48.3 %) at 2 h while ES showed 6.5 % at the same experimental conditions. The pseudo-second-order model kinetic and Langmuir model isotherm provided better-fitting models for the adsorption behavior of P. The adsorption capacity using Langmuir model was 72.0 mg g−1, and the pseudo-second-order kinetic model assumes that the removal process of adsorbate is controlled by chemical adsorption. These results show that the Ca(OH)2 is responsible for the phosphate removal by ligand exchange followed by precipitation mechanism leading to the formation of apatite.

Rapid urbanization has resulted in often unplanned increases in population, and food demand in cities. Historically, hinterlands to these cities have acted as breadbaskets producing food to the urban residents. Accordingly, a large amount of available freshwater has been needed to support these croplands. However, the rapid expansion of cities in developing countries has significantly changed both the croplands around cities and the water demand. It is thus important to quantitatively investigate the water-food nexus of cities related to the changing hinterland agriculture. Water footprint is an indicator reflecting the human impact on water. In this study, we quantified both the blue and green water footprint of major crop products in Suzhou city, China using a bottom-up accounting method. A novel decomposition analysis was carried out with a Logarithmic Mean Divisia Index (LMDI) method to study the driving forces that changed the water footprint during the period 2001-2010. The drivers were designed to reflect the factors related to farmland, such as yield and crop area. This is different from previous decomposition analyses, which focused on economic factors such as GDP. The results show that the crop water footprint of Suzhou city has seen a general decreasing trend between 2001 and 2010. The decomposition analysis showed that the decline of crop area was the main driver that decreased the crop water footprint, followed by the virtual water content (water consumption per unit of production). In contrast the changes of crop combination and yield contributed to an increase in the crop water footprint. Although the shrink of urban croplands decreased the water footprint of crop products. Cities’ increasing demand for food will increase the crop water footprint of consumption. This will increase the dependence of cities on external water footprint of crop products (water embodied in imported crops), which may impact upon food security in cities in the long term.

This paper describes the use of native and protonated grapefruit biomass, a by-product of the food industry, as an effective and low-cost biosorbent for cadmium removal from aqueous solutions. The biomass composition was analysed by high-performance liquid chromatography, scanning electron microscopy coupled with energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy, showing that hydroxyl and carboxylic groups were the main functional groups implicated in Cd(II) biosorption. The effect of different parameters affecting the biosorption process were studied. The optimum removal of cadmium ions was at pH 4.5. Elution of alkaline-earth ions proved to be related with cadmium uptake, aiming for an ion-exchange mechanism. Protonated biomass showed higher adsorption affinity, binding strength and irreversibility for cadmium than native grapefruit, although the optimum metal uptake and high reaction rate was for the native form of grapefruit. Biosorption experimental data fitted Freundlich > Langmuir > Temkin equilibrium adsorption models. Data for both types of biomass were better fitted by a pseudo-second-order kinetic model, with an excellent correlation between calculated and experimental values. Because of these experimental results, and taking into account that both types of biomass displayed an exothermic and spontaneous physical adsorption process, native grapefruit can be proposed in further experiments as a cheap, effective, low-cost and environmentally friendly natural sorbent for the removal of cadmium from industrial wastewater effluents, avoiding chemical pretreatment before its use.

This work aims to evaluate from an energy and economic perspective the production of essential oil, pectin, and biogas as alternatives to valorize orange peel waste. For this, the chemical characterization, extraction of essential oil, and pectin of industrial of this residue samples were done. Moreover, the remaining solid was used to produce biogas. The experimental results were used as input data to simulate the biorefinery. The mass and energy balances from the simulation were used to perform energy and economic analysis of the biorefinery system analyzing the net present value and processing scale as determining factors. Also, mass and energy efficiency indicators were applied to evaluate the performance of the biorefinery. The experimental essential oil, pectin extraction, and biogas yields 0.61% w/w (wet basis), 10.35% w/w (wet basis), and 89.39 Nm3/ton OPW mL biogas/g VS with a CH4 content of 66.73% (59.6 Nm3/ton OPW), respectively. The mass and energy indicators show a good performance of the process in terms of mass and energy efficiency indicators. Moreover, the economic analysis leads to observe that the proposed biorefinery is only feasible at low processing scales. In a conclusion, orange peel waste is a potential feedstock to obtain value-added products such as essential oil and pectin and energy vectors such as biogas in an energy and economic feasible way at low scales allowing the implementation of small-scale integrated biorefinery systems.

AbstractThis article first proposes a reduction strategy of the activated sludge process model with alternated aeration. Initiated with the standard activated sludge model (ASM1), the reduction is based on some biochemical considerations followed by linear approximations of nonlinear terms. Two submodels are then obtained, one for the aerobic phase and one for the anoxic phase, using four state variables related to the organic substrate concentration, the ammonium and nitrate‐nitrite nitrogen, and the oxygen concentration. Then, a two‐step robust estimation strategy is used to estimate both the unmeasured state variables and the unknown inflow ammonium nitrogen concentration. Parameter uncertainty is considered in the dynamics and input matrices of the system. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009

Small islands face difficult challenges to guarantee energy, freshwater and food supply, and sustainable development. The urge to meet their needs, together with the mitigation and adaptation plans to address climate change, have led them to develop renewable energy systems, with a special interest in Ocean Thermal Energy Conversion (OTEC) in tropical islands. Deep Ocean Water (DOW) is a resource that can provide electricity (through OTEC in combination with warm surface water), low temperatures for refrigeration, and nutrients for food production. In this paper we propose an Ocean Technology Ecopark (OTEP) as an integral solution for small islands that consists of an OTEC plant, other alternative uses of DOW, and a Research and Development (R&D) center. We present an application of OTEP to San Andres, a Colombian island that meets all the necessary conditions for the implementation of OTEC technology, water desalinization, and a business model for DOW. We present the main entrance barriers and a four-stage roadmap for the consolidation and sustainability of the OTEP.

Abstract Latent heat thermal energy storage (TES) with phase change materials (PCM) has been incorporated in domestic hot water (DHW) systems, frequently inside the water storage tank, as a way to improve its efficiency. The main challenge for further studies about optimization and design relies on finding accurate energy and exergy models capable of predicting diverse operating cycles with reduced computational resources. This paper describes the simulation and experimental validation of a PCM storage tank under multiple operational scenarios required in practice. Paraffin wax is used as PCM, contained in cylindrical bottles, to store and release energy during solid–liquid phase transformation. Simulation is addressed by using an integrated approach with both analytical and numerical methods, in which classic thermodynamic and heat transfer techniques are used to model the tank and the working fluid, and a finite difference formulation of the two-dimensional enthalpy method is implemented for the PCM. Experimental results were obtained by testing the system in laboratory conditions with different full 24-hour typical operating cycles, considering constant or variable inlet conditions during the thermal charging process along with constant flow rate discharge or batch-wise discharge. Predictions are in good agreement with experimental data. Lastly, the effects of key design parameters on the energy and exergy efficiencies of the PCM storage tank are also evaluated under different scenarios via parametric analysis of the model. Parameters considered in this study include the properties of PCM (mean melting temperature and latent heat of fusion), water flow rate, aspect ratio of the tank, and percentage of PCM inside the tank.

This paper identifies and assesses the economic value of the main natural benefits relating to the complex system of wetlands (CSW) belonging to the San Juan River in the Colombian Magdalena Medio. This is a region rich in biodiversity and natural resources, which in the past was hit by violence and the actions of different armed groups. Benefit estimation takes into account diverse monetary valuation techniques, such as market prices for direct wetland uses and the transfer of benefits, for the assessment of indirect use and non-use values. The results reveal that the most important values relate to ecotourism (60.1%) as a possible future use of the CSW, the benefit of preventing flooding (28.4%), and the biodiversity that inhabits the area (6.7%). All three values represent the total economic value of the CSW. This research also finds that the benefits of the ecosystems currently provided by the CSW exceed the opportunity cost, represented by the total conversion of the area to livestock. Lastly, the net present value (NPV) of 25 and 75 years, relating to the benefits of the CSW, exceeds the income from the conversion of land to livestock, revealing profitable investments in conservation and ecotourism projects.